Good luck on finding anything. Everyone is just guessing. Only go-ogle knows, and I suspect they revise stuff like that anyway. How else to explain rapid improvements and demotions in SERP for your pages?

Neither is conclusive. Your best bet is to experiment. Write 2 similar articles. Target 2 or more keyword phrases in each article that is at least 1000 words. Each paragraph should have one of your targeted keywords and it should also be in your title and url. Do this and you will get indexed quicker, no matter what the keyword is you are targeting.